Whole Building Energy Simulation and Energy Saving Potential Analysis of a Large Public Building

By comparing EnergyPlus with other energy simulation tools, this paper explores how to use EnergyPlus to construct models to accurately simulate complex building systems as well as the interrelationships among sub-systems such as HVAC, lighting and service hot water systems. Then energy consumption and cost of a large public building is simulated and calculated for LEED certification using EnergyPlus. ASHRAE baseline model is constructed according to ASHRAE 90.1 standard and the comparison of annual energy consumption between ASHRAE baseline model and proposed model is carried out. Moreover, an energy efficiency model is built based on the design model. In this model, shading performance of the transparent envelopes and operating performance of the building system components are improved. Meanwhile, other ECMs (energy saving measures) such as daylighting dimming and occupant sensors are considered. The simulation results show 4.7% electricity consumption decrease but 6.9% gas consumption increase of the energy efficiency model compared to ASHRAE baseline model. In summary, the annual energy cost of the energy efficiency model is reduced by 7.75%. INTRODUCTION In a public building, there exist many spaces with quite different functions and structures which will certainly lead to more complicated building systems such as HVAC system, electric lighting system as well as service hot water system. Especially when more and more advanced building technologies become an important part of the composition of a large public building, it does show great difficulty in analyzing and evaluating the whole building energy consumption. EnergyPlus, which is a new generation building energy analysis tool, bears many advantages when compared to its ancestors and is suited to analyze building performances with non-normal building systems especially for large office buildings. Griffith et al employed EnergyPlus to study the influence of some advanced building technologies over the building performance of a public building in Teterboro airport and DOE-2.1 to analyze the effect of such common measures as optimized envelope system and schedules (Griffith et al. 2003). Ellis and Torcellini carried out research on the reliability of EnergyPlus in simulating tall buildings and the outcomes from their research proved accuracy and reliability of EnergyPlus in simulating tall buildings (Ellis and Torcellini 2005). Pan et al. analyzed a campus building equipped with a BCHP system based on the fully understanding of corresponding features of EnergyPlus and also studied its whole building energy and operation performance (Hartkopf et al. 2003 and Pan et al. 2005). This paper first compares EnergyPlus to DOE-2.1 and TRNSYS over their capabilities in modeling buildings and their systems to find out the advantages of EnergyPlus as a whole building energy analysis tool. Then a large public building located in Shanghai is simulated with EnergyPlus as an example to explore how to properly simulate building subsystems and their corresponding control strategies. The simulation results of this building are analyzed. COMPARISON OF ENERGY SIMULATION TOOLS EnergyPlus is an hourly energy simulation engine which employs a simultaneous load/system/plant simulation methodology. In load calculation, CTF method is used to calculate heat conduction through envelopes and then a heat balance method for zone load (Crawley et al. 2001 and Crawley et al. 2005). Moreover, EnergyPlus makes use of a modular, loop-based method to simulate HVAC systems which helps accelerate the model construction process (Strand and Pedersen 2001). Through the object of “Setpoint Manager” in EnergyPlus, many different kinds of variables such as supply air temperature and chilled water supply temperature can be controlled and this function facilitates the construction of modern advanced supervisory control system which Eleventh International IBPSA Conference Glasgow, Scotland July 27-30, 2009